feat: Enhance PostgreSQL type handling and migration scripts

- Introduced equivalent base types and variants for PostgreSQL types to normalize type comparisons.
- Added functions for normalizing SQL types and retrieving equivalent type variants.
- Updated migration writer to handle type alterations with checks for existing types.
- Implemented logic to create necessary extensions (e.g., pg_trgm) based on schema requirements.
- Enhanced tests to cover new functionality for type normalization and migration handling.
- Improved handling of GIN indexes to use appropriate operator classes based on column types.

cmd/relspec/merge.go

@@ -258,6 +258,11 @@ func runMerge(cmd *cobra.Command, args []string) error {
 	fmt.Fprintf(os.Stderr, "      ✓ Merge complete\n\n")
 	fmt.Fprintf(os.Stderr, "%s\n", merge.GetMergeSummary(result))
 
+	if strings.EqualFold(mergeOutputType, "pgsql") && len(result.TypeConflicts) > 0 {
+		return fmt.Errorf("merge detected conflicting existing column types and cannot safely continue with pgsql output\n%s",
+			merge.GetColumnTypeConflictSummary(result, 10))
+	}
+
 	// Step 4: Write output
 	fmt.Fprintf(os.Stderr, "\n[4/4] Writing output...\n")
 	fmt.Fprintf(os.Stderr, "      Format: %s\n", mergeOutputType)

cmd/relspec/merge_from_list_test.go

@@ -3,6 +3,7 @@ package main
 import (
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 )
 
@@ -160,3 +161,38 @@ func TestRunMerge_FromListMissingSourceType(t *testing.T) {
 		t.Error("expected error when neither --source-path nor --from-list is provided")
 	}
 }
+
+func TestRunMerge_PgsqlOutputRejectsColumnTypeConflict(t *testing.T) {
+	saved := saveMergeState()
+	defer restoreMergeState(saved)
+
+	dir := t.TempDir()
+	targetFile := filepath.Join(dir, "target.json")
+	sourceFile := filepath.Join(dir, "source.json")
+	writeTestJSONWithSingleColumnType(t, targetFile, "users", "integer")
+	writeTestJSONWithSingleColumnType(t, sourceFile, "users", "uuid")
+
+	mergeTargetType = "json"
+	mergeTargetPath = targetFile
+	mergeTargetConn = ""
+	mergeSourceType = "json"
+	mergeSourcePath = sourceFile
+	mergeSourceConn = ""
+	mergeFromList = nil
+	mergeOutputType = "pgsql"
+	mergeOutputPath = ""
+	mergeOutputConn = "postgres://relspec:secret@localhost/testdb"
+	mergeSkipTables = ""
+	mergeReportPath = ""
+
+	err := runMerge(nil, nil)
+	if err == nil {
+		t.Fatal("expected pgsql output merge to fail on column type conflict")
+	}
+	if !strings.Contains(err.Error(), "column type conflicts detected") {
+		t.Fatalf("expected conflict summary in error, got: %v", err)
+	}
+	if !strings.Contains(err.Error(), "public.users.id") {
+		t.Fatalf("expected conflicting column path in error, got: %v", err)
+	}
+}

cmd/relspec/testhelpers_test.go

@@ -71,6 +71,40 @@ func writeTestJSON(t *testing.T, path string, tableNames []string) {
 	}
 }
 
+func writeTestJSONWithSingleColumnType(t *testing.T, path, tableName, columnType string) {
+	t.Helper()
+
+	db := minimalDatabase{
+		Name: "test_db",
+		Schemas: []minimalSchema{{
+			Name: "public",
+			Tables: []minimalTable{{
+				Name:   tableName,
+				Schema: "public",
+				Columns: map[string]minimalColumn{
+					"id": {
+						Name:          "id",
+						Table:         tableName,
+						Schema:        "public",
+						Type:          columnType,
+						NotNull:       true,
+						IsPrimaryKey:  true,
+						AutoIncrement: true,
+					},
+				},
+			}},
+		}},
+	}
+
+	data, err := json.Marshal(db)
+	if err != nil {
+		t.Fatalf("failed to marshal test JSON: %v", err)
+	}
+	if err := os.WriteFile(path, data, 0644); err != nil {
+		t.Fatalf("failed to write test file %s: %v", path, err)
+	}
+}
+
 // convertState captures and restores all convert global vars.
 type convertState struct {
 	sourceType    string